Field of the Invention
This invention relates to a method for extending a wafer-supporting sheet of a wafer-supporting table for dicing. 2. Description of the Related Art
Mounting of a semiconductor chip starts with dividing a wafer, which has been determined as being a defect-free product by test, into chips. This dividing process is known as "dicing". FIGS. 8 and 9(A) show a conventional dicing method in which a wafer-supporting table 3 for dicing has a ring shaped frame 1 made of metal such as stainless and having a circular opening portion 1a, and a wafer-supporting sheet 2 attached to a lower surface of the frame 1 by an adhesive (not shown). The supporting sheet 2 has a circular shape and is made of such as vinyl chloride. A wafer 4 is supported (adhered) via an adhesive (not shown) on a central portion of an upper surface of the sheet 2, and is cut into chips by means of a dicing blade (not shown). Then, defect-free chips are picked up by a vacuum head (not shown), and are moved to a next step (for example, a loading step in which the chips are loaded on a circuit board). In this case, a gap between the neighboring chips is small just after the wafer 4 have been dicied into the chips. Therefore, when a chip is picked up by a vacuum head, the chip may contact a neighboring chip, and hence the neighboring chip may be displaced from its original position. As a result, the neighboring chip may fail to be picked up.
To avoid such a problem, a pair of extension rings 5 and 6 are used to widen the gap between neighboring chips, as is shown in FIGS. 8 and 9(A). Specifically, there are provided a first extension ring 5, which is slightly smaller than the frame 1 of the wafer-supporting table 3, and a second extension ring 6, which is slightly smaller than the first extension ring 5. As is shown in FIG. 9(A), the first and second extension rings 5 and 6 are arranged above and under the wafer-supporting sheet 2, respectively. Then, as is shown in FIG. 9(B), the second extension ring 6 is inserted into the opening portion 1a of the frame 1 from the under side thereof, and is pushed up with making an upper surface of the second expansion ring 6 extend the wafer-supporting sheet 2. Finally, as is shown in FIG. 9(C), the first extension ring 5 is fitted onto the second extension ring 6 from above the frame 1 with the wafer-supporting sheet 2 being interposed therebetween. In this state, the sheet 2 is extended by two times a total of the widths of the extension rings 5 and 6, and the gap between the neighboring chips is increased in accordance with the amount of extension.
However, since the conventional wafer-supporting-sheet extending method uses two tools (=the extension rings 5 and 6) to extend the wafer-supporting sheet 2, manufacturing cost is greater than in a case where only a single tool is used. Further, since the sheet 2 is extended in a direction perpendicular to its supporting surface, the widths of the rings 5 and 6 must be increased in order to increase the amount of extension of the sheet 2 so that a total height of the wafer-supporting table 3 in a state as shown in FIG. 9(C) (i.e., the width of each of the rings 5 and 6, two times the thickness of the sheet 2, and the thickness of the wafer 4) becomes large. As a result, a large space is necessary to storage a plurality of wafer-supporting tables 3 (each of which is in the state shown in FIG. 9(C) while they are arranged in a vertical direction with they being held in a horizontal posture.